470 MISSES K. FOOT AND E. C. STROBELL : 



The meau length of the intromittent organ computed from the total 

 number of F2 males (190 specimens) is 124*42 mm. A comparison of this 

 with the mean length of the organ of the F^ hybrids (124'9 mm.) shows that 

 the mean length is almost the same for both the first and second generations, 

 differing only by a few hundredths of a millimetre. It is clear therefore 

 that the F2 generation, like the Fi, is intermediate in size, and both agree 

 further in showing a stronger inheritance from variolarhis than from servus. 

 This is true not only when the total number of Fg hybrids is considered, but 

 holds for each individual family of the F2 generation — each of the seven 

 families has a mean length of intromittent organ which is below the 

 theoretical intermediate between the parent species (131*55 mm.). 



" Sixth. Both extremes in size of the original j^^ii'^nts may he found in the 

 F<2 generation, hit not in the F^ generation.^' — As the two characters we are 

 testing are exclusively male^ we can compare our results with the above 

 observation only in the case of the original male parent. The length of the 

 intromittent organ of the original F. servvs male parent of the first cross is 

 1G6 mm., a length which has not been reached in any of the 190 specimens 

 of the F2 generation, the longest intromittent organ of all these F2 hybrids 

 measuring only 152 mm. (Table 3), and in only one specimen of the 190 was 

 this length attained. We therefore cannot say that the length of the intro- 

 mittent organ of this grandparent is found in our F2 generation. If we 

 disregard this length and take into consideration the mean length of the 

 organ both in servus and in variolarius, we then find that a length of intro- 

 mittent organ characteristic of both species is represented in the F2 generation, 

 and we find a still larger number like the two species, if we consider all 

 the F2 hybrids which have a length of organ within the limits of length 

 cliaracteristic of variolarius and servus. For example, 14 F2 hybrids are like 

 variolarius in having the length of intromittent organ 106 mm. or less, and 

 7 are like serous in having the length of intromittent organ 146 mm. or 

 more (Tables 3 to 10). 



Among the ten Fi hybrids we find none with a length of organ like 

 E. variolarius (106 mm. or less) nor any like E. servus (146 mm. or more), 

 but we are inclined to believe that this is due to the relatively small number 

 of specimens. As stated above, the relative number of variations in length of 

 the intromittent organ of the ten Fi hybrids is greater than that of the Fg 

 generation, and therefore we should expect a larger number of specimens 

 to give us a larger range of variation. Even among these ten specimens we 

 have one with the intromittent organ only 109 mm. long, and this is within 

 3 mm. of the variolarius type. 



The results in the case of the genital spot are very similar. Nine of the 

 eleven Fi hybrids have a spot variably intermediate between that of the two 

 parent species, but two are like servus in having no spot. 



